The Pittsburgh region — which includes all Southwestern Pennsylvania counties and some nearby counties in West Virginia and Ohio — saw 11 tornadoes on Oct. 21. And the Cleveland region — which includes many Northwest Ohio counties and Erie and Crawford counties in Pennsylvania — saw eight tornadoes on Oct. 21.
According to the National Weather Service, thunderstorms between 4:30 p.m. and 6:30 p.m. on Oct. 21 produced eight tornadoes across portions of Northeast Ohio. The storm, which apparently also caused tornadoes in the Pittsburgh region, was a "potent upper-level" event that was associated with a cold front moving east across the region. One of the tornadoes in the Cleveland region, an EF-1, reached estimated wind speeds of 110 mph.
With our 11 tornadoes on October 21st, that makes 19 total tornadoes for this event across the Ohio River Valley. That was quite an outbreak! https://t.co/HaAkRjIOLt— NWS Pittsburgh (@NWSPittsburgh) November 5, 2021
According to data from Mississippi State University, these 19 tornadoes are the most by far that the Cleveland and Pittsburgh regions have seen in October, in documented history.
According to data that tracks back to 1880, Pittsburgh has seen a total of 10 tornadoes in the month of October. On a single day in Oct. 2021, that total was more than doubled. The same goes for Cleveland, which, since 1950, has seen five tornadoes in October, an amount also more than doubled on Oct. 21, 2021. (There is no data for the Cleveland region between 2013-2020.)
“With our 11 tornadoes on October 21st, that makes 19 total tornadoes for this event across the Ohio River Valley,” tweeted the official NWS Pittsburgh account on Nov. 4. “That was quite an outbreak!”
It's unclear what day in documented history saw the most tornadoes for the combined Pittsburgh and Cleveland regions. According to data, 1998 was the year that saw the most tornadoes in the Pittsburgh region's history. On June 2, 1998, there were 11 tornadoes across the region. The Cleveland region didn’t see any that day.
In the Cleveland region, July 12, 1992 saw several more tornadoes compared to Oct. 21. According to the Mississippi State data, there were 19 tornadoes in the greater Cleveland region, including an EF-3 tornado in Summit County, Ohio. On this same day, the Pittsburgh region saw two tornadoes. The 21 combined total tornadoes amount to two more than on Oct. 21, 2021.
Data also appears to show tornadoes becoming more frequent in the Pittsburgh region. In the last five years, the Pittsburgh region has seen at least 10 tornadoes each year. This is the longest stretch of Pittsburgh seeing at least 10 tornadoes a year in documented history.
Scientists agree that greenhouse gas emissions and subsequent climate change is leading many parts of the world to experience more severe and more frequent storms. Costa Samaras of Carnegie Mellon University told City Paper in 2018 that as the climate continues to warm, Pittsburghers should expect more severe storms, which will likely cause more power outages.
NWS Pittsburgh says that since the Oct. 21 tornado outbreak, the office has talked about building a better database to answer questions on tornado statistics.